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原创最新推荐文章于 2026-03-06 00:08:12 发布 2.1k 阅读 AI 写同款· GEO 优化 ›

【Oracle】Oracle查询表占用的空间（表大小）【代码】Oracle查询表占用的空间（表大小）阅读详情

######### 创建数据库----look $ORACLE_HOME/rdbms/admin/buildall.sql #############

create database db01
maxlogfiles 10
maxdatafiles 1024
maxinstances 2
logfile
GROUP 1 ('/u01/oradata/db01/log_01_db01.rdo') SIZE 15M,
GROUP 2 ('/u01/oradata/db01/log_02_db01.rdo') SIZE 15M,
GROUP 3 ('/u01/oradata/db01/log_03_db01.rdo') SIZE 15M,
datafile 'u01/oradata/db01/system_01_db01.dbf') SIZE 100M,
undo tablespace UNDO
datafile '/u01/oradata/db01/undo_01_db01.dbf' SIZE 40M
default temporary tablespace TEMP
tempfile '/u01/oradata/db01/temp_01_db01.dbf' SIZE 20M
extent management local uniform size 128k
character set AL32UTE8
national character set AL16UTF16
set time_zone='America/New_York';

############### 数据字典 ##########

set wrap off

select * from v$dba_users;

grant select on table_name to user/rule;

select * from user_tables;

select * from all_tables;

select * from dba_tables;

revoke dba from user_name;

shutdown immediate

startup nomount

select * from v$instance;

select * from v$sga;

select * from v$tablespace;

alter session set nls_language=american;

alter database mount;

select * from v$database;

alter database open;

desc dictionary

select * from dict;

desc v$fixed_table;

select * from v$fixed_table;

set oracle_sid=foxconn

select * from dba_objects;

set serveroutput on

execute dbms_output.put_line('sfasd');

############# 控制文件 ###########

select * from v$database;

select * from v$tablespace;

select * from v$logfile;

select * from v$log;

select * from v$backup;

/*备份用户表空间*/
alter tablespace users begin backup;

select * from v$archived_log;

select * from v$controlfile;

alter system set control_files='$ORACLE_HOME/oradata/u01/ctrl01.ctl',
'$ORACLE_HOME/oradata/u01/ctrl02.ctl' scope=spfile;

cp $ORACLE_HOME/oradata/u01/ctrl01.ctl $ORACLE_HOME/oradata/u01/ctrl02.ctl

startup pfile='../initSID.ora'

select * from v$parameter where name like 'control%' ;

show parameter control;

select * from v$controlfile_record_section;

select * from v$tempfile;

/*备份控制文件*/
alter database backup controlfile to '../filepath/control.bak';

/*备份控制文件，并将二进制控制文件变为了asc 的文本文件*/
alter database backup controlfile to trace;

############### redo log ##############

archive log list;

alter system archive log start;--启动自动存档

alter system switch logfile;--强行进行一次日志switch

alter system checkpoint;--强制进行一次checkpoint

alter tablspace users begin backup;

alter tablespace offline;

/*checkpoint 同步频率参数FAST_START_MTTR_TARGET,同步频率越高，系统恢复所需时间越短*/
show parameter fast;

show parameter log_checkpoint;

/*加入一个日志组*/
alter database add logfile group 3 ('/$ORACLE_HOME/oracle/ora_log_file6.rdo' size 10M);

/*加入日志组的一个成员*/
alter database add logfile member '/$ORACLE_HOME/oracle/ora_log_file6.rdo' to group 3;

/*删除日志组:当前日志组不能删；活动的日志组不能删；非归档的日志组不能删*/
alter database drop logfile group 3;

/*删除日志组中的某个成员，但每个组的最后一个成员不能被删除*/
alter databse drop logfile member '$ORACLE_HOME/oracle/ora_log_file6.rdo';

/*清除在线日志*/
alter database clear logfile '$ORACLE_HOME/oracle/ora_log_file6.rdo';

alter database clear logfile group 3;

/*清除非归档日志*/
alter database clear unarchived logfile group 3;

/*重命名日志文件*/
alter database rename file '$ORACLE_HOME/oracle/ora_log_file6.rdo' to '$ORACLE_HOME/oracle/ora_log_file6a.rdo';

show parameter db_create;

alter system set db_create_online_log_dest_1='path_name';

select * from v$log;

select * from v$logfile;

/*数据库归档模式到非归档模式的互换,要启动到mount状态下才能改变;startup mount;然后再打开数据库.*/
alter database noarchivelog/archivelog;

achive log start;---启动自动归档

alter system archive all;－－手工归档所有日志文件

select * from v$archived_log;

show parameter log_archive;

###### 分析日志文件logmnr ##############

1) 在init.ora中set utl_file_dir 参数
2) 重新启动oracle
3) create 目录文件
desc dbms_logmnr_d;
dbms_logmnr_d.build;
4) 加入日志文件 add/remove log file
dhms_logmnr.add_logfile
dbms_logmnr.removefile
5) start logmnr
dbms_logmnr.start_logmnr
6) 分析出来的内容查询 v$logmnr_content --sqlredo/sqlundo

实践：

desc dbms_logmnr_d;

/*对数据表做一些操作，为恢复操作做准备*/
update 表 set qty=10 where stor_id=6380;

delete 表 where stor_id=7066;
/***********************************/
utl_file_dir的路径
execute dbms_logmnr_d.build('foxdict.ora','$ORACLE_HOME/oracle/admin/fox/cdump');

execute dbms_logmnr.add_logfile('$ORACLE_HOME/oracle/ora_log_file6.log',dbms_logmnr.newfile);

execute dbms_logmnr.start_logmnr(dictfilename=>'$ORACLE_HOME/oracle/admin/fox/cdump/foxdict.ora');

######### tablespace ##############

select * form v$tablespace;

select * from v$datafile;

/*表空间和数据文件的对应关系*/
select t1.name,t2.name from v$tablespace t1,v$datafile t2 where t1.ts#=t2.ts#;

alter tablespace users add datafile 'path' size 10M;

select * from dba_rollback_segs;

/*限制用户在某表空间的使用限额*/
alter user user_name quota 10m on tablespace_name;

create tablespace xxx [datafile 'path_name/datafile_name'] [size xxx] [extent management local/dictionary] [default storage(xxx)];

exmple: create tablespace userdata datafile '$ORACLE_HOME/oradata/userdata01.dbf' size 100M AUTOEXTEND ON NEXT 5M MAXSIZE 200M;
create tablespace userdata datafile '$ORACLE_HOME/oradata/userdata01.dbf' size 100M extent management dictionary default storage(initial 100k next 100k pctincrease 10) offline;
/*9i以后，oracle建议使用local管理，而不使用dictionary管理，因为local采用bitmap管理表空间，不会产生系统表空间的自愿争用;*/
create tablespace userdata datafile '$ORACLE_HOME/oradata/userdata01.dbf' size 100M extent management local uniform size 1m;
create tablespace userdata datafile '$ORACLE_HOME/oradata/userdata01.dbf' size 100M extent management local autoallocate;
/*在创建表空间时，设置表空间内的段空间管理模式，这里用的是自动管理*/
create tablespace userdata datafile '$ORACLE_HOME/oradata/userdata01.dbf' size 100M extent management local uniform size 1m segment space management auto;

alter tablespace userdata mininum extent 10;

alter tablespace userdata default storage(initial 1m next 1m pctincrease 20);

/*undo tablespace(不能被用在字典管理模下) */
create undo tablespace undo1 datafile '$ORACLE_HOME/oradata/undo101.dbf' size 40M extent management local;

show parameter undo;

/*temporary tablespace*/
create temporary tablespace userdata tempfile '$ORACLE_HOME/oradata/undo101.dbf' size 10m extent management local;

/*设置数据库缺省的临时表空间*/
alter database default temporary tablespace tablespace_name;

/*系统/临时/在线的undo表空间不能被offline*/
alter tablespace tablespace_name offline/online;

alter tablespace tablespace_name read only;

/*重命名用户表空间*/
alter tablespace tablespace_name rename datafile '$ORACLE_HOME/oradata/undo101.dbf' to '$ORACLE_HOME/oradata/undo102.dbf';

/*重命名系统表空间 ,但在重命名前必须将数据库shutdown,并重启到mount状态*/
alter database rename file '$ORACLE_HOME/oradata/system01.dbf' to '$ORACLE_HOME/oradata/system02.dbf';

drop tablespace userdata including contents and datafiles;---drop tablespce

/*resize tablespace,autoextend datafile space*/
alter database datafile '$ORACLE_HOME/oradata/undo102.dbf' autoextend on next 10m maxsize 500M;

/*resize datafile*/
alter database datafile '$ORACLE_HOME/oradata/undo102.dbf' resize 50m;

/*给表空间扩展空间*/
alter tablespace userdata add datafile '$ORACLE_HOME/oradata/undo102.dbf' size 10m;

/*将表空间设置成OMF状态*/
alter system set db_create_file_dest='$ORACLE_HOME/oradata';

create tablespace userdata;---use OMF status to create tablespace;

drop tablespace userdata;---user OMF status to drop tablespace;

select * from dba_tablespace/v$tablespace/dba_data_files;

/*将表的某分区移动到另一个表空间*/
alter table table_name move partition partition_name tablespace tablespace_name;

###### ORACLE storage structure and relationships #########

/*手工分配表空间段的分区(extend)大小*/
alter table kong.test12 allocate extent(size 1m datafile '$ORACLE_HOME/oradata/undo102.dbf');

alter table kong.test12 deallocate unused; ---释放表中没有用到的分区

show parameter db;

alter system set db_8k_cache_size=10m; ---配置8k块的内存空间块参数

select * from dba_extents/dba_segments/data_tablespace;

select * from dba_free_space/dba_data_file/data_tablespace;

/*数据对象所占用的字节数*/
select sum(bytes) from dba_extents where onwer='kong' and segment_name ='table_name';

############ UNDO Data ################

show parameter undo;

alter tablespace users offline normal;

alter tablespace users offline immediate;

recover datafile '$ORACLE_HOME/oradata/undo102.dbf';

alter tablespace users online ;

select * from dba_rollback_segs;

alter system set undo_tablespace=undotbs1;

/*忽略回滚段的错误提示*/
alter system set undo_suppress_errors=true;

/*在自动管理模式下,不会真正建立rbs1;在手工管理模式则可以建立,且是私有回滚段*/
create rollback segment rbs1 tablespace undotbs;

desc dbms_flashback;

/*在提交了修改的数据后,9i提供了旧数据的回闪操作,将修改前的数据只读给用户看,但这部分数据不会又恢复在表中,而是旧数据的一个映射*/
execute dbms_flashback.enable_at_time('26-JAN-04:12:17:00 pm');

execute dbms_flashback.disable;

/*回滚段的统计信息*/
select end_time,begin_time,undoblks from v$undostat;

/*undo表空间的大小计算公式: UndoSpace=[UR * (UPS * DBS)] + (DBS * 24)
UR :UNDO_RETENTION 保留的时间(秒)
UPS :每秒的回滚数据块
DBS:系统EXTENT和FILE SIZE(也就是db_block_size)*/

select * from dba_rollback_segs/v$rollname/v$rollstat/v$undostat/v$session/v$transaction;

show parameter transactions;

show parameter rollback;

/*在手工管理模式下,建立公共的回滚段*/
create public rollback segment prbs1 tablespace undotbs;

alter rollback segment rbs1 online;----在手工管理模式

/*在手工管理模式中,initSID.ora中指定 undo_management=manual 、rollback_segment=('rbs1','rbs2',...)、
transactions=100 、transactions_per_rollback_segment=10
然后 shutdown immediate ,startup pfile=..../???.ora */

########## Managing Tables ###########

/*char type maxlen=2000;varchar2 type maxlen=4000 bytes
rowid 是18位的64进制字符串 (10个bytes 80 bits)
rowid组成: object#(对象号)--32bits,6位
rfile#(相对文件号)--10bits,3位
block#(块号)--22bits,6位
row#(行号)--16bits,3位
64进制: A-Z,a-z,0-9,/,+ 共64个符号

dbms_rowid 包中的函数可以提供对rowid的解释*/

select rowid,dbms_rowid.rowid_block_number(rowid),dbms_rowid.rowid_row_number(rowid) from table_name;

create table test2
(
id int,
lname varchar2(20) not null,
fname varchar2(20) constraint ck_1 check(fname like 'k%'),
empdate date default sysdate)
) tablespace tablespace_name;

create global temporary table test2 on commit delete/preserve rows as select * from kong.authors;

create table user.table(...) tablespace tablespace_name storage(...) pctfree10 pctused 40;

alter table user.tablename pctfree 20 pctused 50 storage(...);---changing table storage

/*手工分配分区,分配的数据文件必须是表所在表空间内的数据文件*/
alter table user.table_name allocate extent(size 500k datafile '...');

/*释放表中没有用到的空间*/
alter table table_name deallocate unused;

alter table table_name deallocate unused keep 8k;

/*将非分区表的表空间搬到新的表空间,在移动表空间后，原表中的索引对象将会不可用，必须重建*/
alter table user.table_name move tablespace new_tablespace_name;

create index index_name on user.table_name(column_name) tablespace users;

alter index index_name rebuild;

drop table table_name [CASCADE CONSTRAINTS];

alter table user.table_name drop column col_name [CASCADE CONSTRAINTS CHECKPOINT 1000];---drop column

/*给表中不用的列做标记*/
alter table user.table_name set unused column comments CASCADE CONSTRAINTS;

/*drop表中不用的做了标记列*/
alter table user.table_name drop unused columns checkpoint 1000;

/*当在drop col是出现异常，使用CONTINUE，防止重删前面的column*/
ALTER TABLE USER.TABLE_NAME DROP COLUMNS CONTINUE CHECKPOINT 1000;

select * from dba_tables/dba_objects;

######## managing indexes ##########

/*create index*/
example:
/*创建一般索引*/
create index index_name on table_name(column_name) tablespace tablespace_name;
/*创建位图索引*/
create bitmap index index_name on table_name(column_name1,column_name2) tablespace tablespace_name;
/*索引中不能用pctused*/
create [bitmap] index index_name on table_name(column_name) tablespace tablespace_name pctfree 20 storage(inital 100k next 100k) ;
/*大数据量的索引最好不要做日志*/
create [bitmap] index index_name table_name(column_name1,column_name2) tablespace_name pctfree 20 storage(inital 100k next 100k) nologging;
/*创建反转索引*/
create index index_name on table_name(column_name) reverse;
/*创建函数索引*/
create index index_name on table_name(function_name(column_name)) tablespace tablespace_name;
/*建表时创建约束条件*/
create table user.table_name(column_name number(7) constraint constraint_name primary key deferrable using index storage(initial 100k next 100k) tablespace tablespace_name,column_name2 varchar2(25) constraint constraint_name not null,column_name3 number(7)) tablespace tablespace_name;

/*给创建bitmap index分配的内存空间参数，以加速建索引*/
show parameter create_bit;

/*改变索引的存储参数*/
alter index index_name pctfree 30 storage(initial 200k next 200k);

/*给索引手工分配一个分区*/
alter index index_name allocate extent (size 200k datafile '$ORACLE/oradata/..');

/*释放索引中没用的空间*/
alter index index_name deallocate unused;

/*索引重建*/
alter index index_name rebuild tablespace tablespace_name;

/*普通索引和反转索引的互换*/
alter index index_name rebuild tablespace tablespace_name reverse;

/*重建索引时，不锁表*/
alter index index_name rebuild online;

/*给索引整理碎片*/
alter index index_name COALESCE;

/*分析索引,事实上是更新统计的过程*/
analyze index index_name validate structure;

desc index_state;

drop index index_name;

alter index index_name monitoring usage;-----监视索引是否被用到

alter index index_name nomonitoring usage;----取消监视

/*有关索引信息的视图*/
select * from dba_indexes/dba_ind_columns/dbs_ind_expressions/v$object_usage;

########## 数据完整性的管理(Maintaining data integrity) ##########

alter table table_name drop constraint constraint_name;----drop 约束

alter table table_name add constraint constraint_name primary key(column_name1,column_name2);-----创建主键

alter table table_name add constraint constraint_name unique(column_name1,column_name2);---创建唯一约束

/*创建外键约束*/
alter table table_name add constraint constraint_name foreign key(column_name1) references table_name(column_name1);

/*不效验老数据，只约束新的数据[enable/disable：约束/不约束新数据;novalidate/validate:不对/对老数据进行验证]*/
alter table table_name add constraint constraint_name check(column_name like 'B%') enable/disable novalidate/validate;

/*修改约束条件，延时验证，commit时验证*/
alter table table_name modify constraint constraint_name initially deferred;

/*修改约束条件，立即验证*/
alter table table_name modify constraint constraint_name initially immediate;

alter session set constraints=deferred/immediate;

/*drop一个有外键的主键表,带cascade constraints参数级联删除*/
drop table table_name cascade constraints;

/*当truncate外键表时，先将外键设为无效，再truncate;*/
truncate table table_name;

/*设约束条件无效*/
alter table table_name disable constraint constraint_name;

alter table table_name enable novalidate constraint constraint_name;

/*将无效约束的数据行放入exception的表中，此表记录了违反数据约束的行的行号；在此之前，要先建exceptions表*/
alter table table_name add constraint constraint_name check(column_name >15) enable validate exceptions into exceptions;

/*运行创建exceptions表的脚本*/
start $ORACLE_HOME/rdbms/admin/utlexcpt.sql;

/*获取约束条件信息的表或视图*/
select * from user_constraints/dba_constraints/dba_cons_columns;

################## managing password security and resources ####################

alter user user_name account unlock/open;----锁定/打开用户;

alter user user_name password expire;---设定口令到期

/*建立口令配置文件,failed_login_attempts口令输多少次后锁，password_lock_times指多少天后口令被自动解锁*/
create profile profile_name limit failed_login_attempts 3 password_lock_times 1/1440;
/*创建口令配置文件*/
create profile profile_name limit failed_login_attempts 3 password_lock_time unlimited password_life_time 30 password_reuse_time 30 password_verify_function verify_function password_grace_time 5;
/*建立资源配置文件*/
create profile prfile_name limit session_per_user 2 cpu_per_session 10000 idle_time 60 connect_time 480;

alter user user_name profile profile_name;

/*设置口令解锁时间*/
alter profile profile_name limit password_lock_time 1/24;

/*password_life_time指口令文件多少时间到期，password_grace_time指在第一次成功登录后到口令到期有多少天时间可改变口令*/
alter profile profile_name limit password_lift_time 2 password_grace_time 3;

/*password_reuse_time指口令在多少天内可被重用,password_reuse_max口令可被重用的最大次数*/
alter profile profile_name limit password_reuse_time 10[password_reuse_max 3];

alter user user_name identified by input_password;-----修改用户口令

drop profile profile_name;

/*建立了profile后，且指定给某个用户，则必须用CASCADE才能删除*/
drop profile profile_name CASCADE;

alter system set resource_limit=true;---启用自愿限制,缺省是false

/*配置资源参数*/
alter profile profile_name limit cpu_per_session 10000 connect_time 60 idle_time 5;
/*资源参数(session级)
cpu_per_session 每个session占用cpu的时间单位1/100秒
sessions_per_user 允许每个用户的并行session数
connect_time 允许连接的时间单位分钟
idle_time 连接被空闲多少时间后，被自动断开单位分钟
logical_reads_per_session 读块数
private_sga 用户能够在SGA中使用的私有的空间数单位bytes

(call级)
cpu_per_call 每次(1/100秒)调用cpu的时间
logical_reads_per_call 每次调用能够读的块数
*/

alter profile profile_name limit cpu_per_call 1000 logical_reads_per_call 10;

desc dbms_resouce_manager;---资源管理器包

/*获取资源信息的表或视图*/
select * from dba_users/dba_profiles;

###### Managing users ############

show parameter os;

create user testuser1 identified by kxf_001;

grant connect,createtable to testuser1;

alter user testuser1 quota 10m on tablespace_name;

/*创建用户*/
create user user_name identified by password default tablespace tablespace_name temporary tablespace tablespace_name quota 15m on tablespace_name password expire;

/*数据库级设定缺省临时表空间*/
alter database default temporary tablespace tablespace_name;

/*制定数据库级的缺省表空间*/
alter database default tablespace tablespace_name;

/*创建os级审核的用户，需知道os_authent_prefix，表示oracle和os口令对应的前缀,'OPS$'为此参数的值，此值可以任意设置*/
create user user_name identified by externally default OPS$tablespace_name tablespace_name temporary tablespace tablespace_name quota 15m on tablespace_name password expire;

/*修改用户使用表空间的限额,回滚表空间和临时表空间不允许授予限额*/
alter user user_name quota 5m on tablespace_name;

/*删除用户或删除级联用户(用户对象下有对象的要用CASCADE，将其下一些对象一起删除)*/
drop user user_name [CASCADE];

/*每个用户在哪些表空间下有些什么限额*/
desc dba_ts_quotas;select * from dba_ts_quotas where username='...';

/*改变用户的缺省表空间*/
alter user user_name default tablespace tablespace_name;

######### Managing Privileges #############

grant create table,create session to user_name;

grant create any table to user_name; revoke create any table from user_name;

/*授予权限语法,public 标识所有用户,with admin option允许能将权限授予第三者的权限*/
grant system_privs,[......] to [user/role/public],[....] [with admin option];

select * from v$pwfile_users;

/*当 O7_dictionary_accessiblity参数为True时，标识select any table时，包括系统表也能select ,否则，不包含系统表;缺省为false*/
show parameter O7;

/*由于 O7_dictionary_accessiblity为静态参数，不能动态改变，故加scope=spfile,下次启动时才生效*/
alter system set O7_dictionary_accessiblity=true scope=spfile;

/*授予对象中的某些字段的权限，如select 某表中的某些字段的权限*/
grant [object_privs(column,....)],[...] on object_name to user/role/public,... with grant option;

/*oracle不允许授予select某列的权限,但可以授insert ,update某列的权限*/
grant insert(column_name1,column_name2,...) on table_name to user_name with grant option;

select * from dba_sys_privs/session_privs/dba_tab_privs/user_tab_privs/dba_col_privs/user_col_privs;

/*db/os/none 审计被记录在数据库/操作系统/不审计缺省是none*/
show parameter audit_trail;

/*启动对表的select动作*/
audit select on user.table_name by session;

/*by session在每个session中发出command只记录一次，by access则每个command都记录*/
audit [create table][select/update/insert on object by session/access][whenever successful/not successful];

desc dbms_fga;---进一步设计，则可使用dbms_fgs包

/*取消审计*/
noaudit select on user.table_name;

/*查被审计信息*/
select * from all_def_audit_opts/dba_stmt_audit_opts/dba_priv_audit_opts/dba_obj_audit_opts;

/*获取审计记录*/
select * from dba_audit_trail/dba_audit_exists/dba_audit_object/dba_audit_session/dba_audit_statement;

########### Managing Role #################

create role role_name; grant select on table_name to role_name; grant role_name to user_name; set role role_name;

create role role_name;
create role role_name identified by password;
create role role_name identified externally;

set role role_name ; ----激活role
set role role_name identified by password;

alter role role_name not identified;
alter role role_name identified by password;
alter role role_name identified externally;

grant priv_name to role_name [WITH ADMIN OPTION];
grant update(column_name1,col_name2,...) on table_name to role_name;
grant role_name1 to role_name2;

/*建立default role,用户登录时，缺省激活default role*/
alter user user_name default role role_name1,role_name2,...;
alter user user_name default role all;
alter user user_name default role all except role_name1,...;
alter user user_name default role none;

set role role1 [identified by password],role2,....;
set role all;
set role except role1,role2,...;
set role none;

revoke role_name from user_name;
revoke role_name from public;

drop role role_name;

select * from dba_roles/dba_role_privs/role_role_privs/dba_sys_privs/role_sys_privs/role_tab_privs/session_roles;

########### Basic SQL SELECT ################

select col_name as col_alias from table_name ;

select col_name from table_name where col1 like '_o%'; ----'_'匹配单个字符

/*使用字符函数(右边截取,字段中包含某个字符,左边填充某字符到固定位数,右边填充某字符到固定位数)*/
select substr(col1,-3,5),instr(col2,'g'),LPAD(col3,10,'$'),RPAD(col4,10,'%') from table_name;

/*使用数字函数(往右/左几位四舍五入,取整,取余)*/
select round(col1,-2),trunc(col2),mod(col3) from table_name ;

/*使用日期函数(计算两个日期间相差几个星期,两个日期间相隔几个月,在某个月份上加几个月,某个日期的下一个日期,
某日期所在月的最后的日期,对某个日期的月分四舍五入，对某个日期的月份进行取整)*/
select (sysdate-col1)/7 week,months_between(sysdate,col1),add_months(col1,2),next_day(sysdate,'FRIDAY'),last_day(sysdate),
round(sysdate,'MONTH'),trunc(sysdate,'MONTH') from table_name;

/*使用NULL函数(当expr1为空取expr2/当expr1为空取expr2,否则取expr3/当expr1=expr2返回空)*/
select nvl(expr1,expr2),nvl2(expr1,expr2,expr3),nullif(expr1,expr2) from table_name;

select column1,column2,column3, case column2 when '50' then column2*1.1
when '30' then column2*2.1
when '10' then column3/20
else column3
end as ttt
from table_name ; ------使用case函数

select table1.col1,table2.col2 from table1
[CROSS JOIN table2] | -----笛卡儿连接
[NATURAL JOIN table2] | -----用两个表中的同名列连接
[JOIN table2 USING (column_name)] | -----用两个表中的同名列中的某一列或几列连接
[JOIN table2
ON (table1.col1=table2.col2)] |
[LEFT|RIGHT|FULL OUTER JOIN table2 ------相当于(+)=,=(+)连接,全外连接
ON (table1.col1=table2.col2)]; ------SQL 1999中的JOIN语法;

example:
select col1,col2 from table1 t1
join table2 t2
on t1.col1=t2.col2 and t1.col3=t2.col1
join table3 t3
on t2.col1=t3.col3;

select * from table_name where col1 < any (select col2 from table_name2 where continue group by col3);

select * from table_name where col1 < all (select col2 from table_name2 where continue group by col3);

insert into (select col1,col2,col3 form table_name where col1> 50 with check option) values (value1,value2,value3);

MERGE INTO table_name table1
USING table_name2 table2
ON (table1.col1=table2.col2)
WHEN MATCHED THEN
UPDATE SET
table1.col1=table2.col2,
table1.col2=table2.col3,
...
WHEN NOT MATCHED THEN
INSERT VALUES(table2.col1,table2.col2,table2.col3,...); -----合并语句

##################### CREATE/ALTER TABLE #######################

alter table table_name drop column column_name ;---drop column

alter table table_name set unused (col1,col2,...);----设置列无效，这个比较快。
alter table table_name drop unused columns;---删除被设为无效的列

rename table_name1 to table_name2; ---重命名表

comment on table table_name is 'comment message';----给表放入注释信息

create table table_name
(col1 int not null,col2 varchar2(20),col3 varchar2(20),
constraint uk_test2_1 unique(col2,col3))); -----定义表中的约束条件

alter table table_name add constraint pk_test2 primary key(col1,col2,...); ----创建主键

/*建立外键*/
create table table_name (rid int,name varchar2(20),constraint fk_test3 foreign key(rid) references other_table_name(id));

alter table table_name add constraint ck_test3 check(name like 'K%');

alter table table_name drop constraint constraint_name;

alter table table_name drop primary key cascade;----级联删除主键

alter table table_name disable/enable constraint constraint_name;----使约束暂时无效

/*删除列，并级联删除此列下的约束条件*/
alter table table_name drop column column_name cascade constraint;

select * from user_constraints/user_cons_columns;---约束条件相关视图

############## Create Views #####################

CREATE [OR REPLACE] [FORCE|NOFORCE] VIEW view_name [(alias[,alias]...)]
AS subquery
[WITH CHECK OPTION [CONSTRAINT constraint_name]]
[WITH READ ONLY [CONSTRAINT constraint_name]]; ------创建视图的语法

example: Create or replace view testview as select col1,col2,col3 from table_name; ------创建视图
/*使用别名*/
Create or replace view testview as select col1,sum(col2) col2_alias from table_name;
/*创建复杂视图*/
Create view view_name (alias1,alias2,alias3,alias4) as select d.col1,min(e.col1),max(e.col1),avg(e.col1) from table_name1 e,table_name2 d where e.col2=d.col2 group by d.col1;
/*当用update修改数据时，必须满足视图的col1>10的条件，不满足则不能被改变.*/
Create or replace view view_name as select * from table_name where col1>10 with check option;

/*改变视图的值.对于简单视图可以用update语法修改表数据，但复杂视图则不一定能改。如使用了函数，group by ,distinct等的列*/
update view_name set col1=value1;

/*TOP-N分析*/
select [column_list],rownum from (select [column_list] from table_name order by Top-N_column) where rownum<=N;

/*找出某列三条最大值的记录*/
example: select rownum as rank ,col1 ,col2 from (select col1 ,col2 from table_name order by col2 desc) where rownum<=3;

############# Other database Object ###############

CREATE SEQUENCE sequence_name [INCREMENT BY n]
[START WITH n]
[{MAXVALUE n | NOMAXVALUE}]
[{MINVALUE n | NOMINVALUE}]
[{CYCEL | NOCYCLE}]
[{CACHE n | NOCACHE}]; -----创建SEQUENCE

example:
CREATE SEQUENCE sequence_name INCREMENT BY 10
START WITH 120
MAXVALUE 9999
NOCACHE
NOCYCLE;

select * from user_sequences ;---当前用户下记录sequence的视图

select sequence_name.nextval,sequence_name.currval from dual;-----sequence的引用

alter sequence sequence_name INCREMENT BY 20
MAXVALUE 999999
NOCACHE
NOCYCLE; -----修改sequence,不能改变起始序号

drop sequence sequence_name; ----删除sequence

CREATE [PUBLIC] SYNONYM synonym_name FOR object; ------创建同义词

DROP [PUBLIC] SYNONYM synonym_name;----删除同义词

CREATE PUBLIC DATABASE LINK link_name USEING OBJECT;----创建DBLINK

select * from object_name@link_name; ----访问远程数据库中的对象

/*union 操作，它将两个集合的交集部分压缩，并对数据排序*/
select col1,col2,col3 from table1_name union select col1,col2,col3 from table2_name;

/*union all 操作，两个集合的交集部分不压缩，且不对数据排序*/
select col1,col2,col3 from table1_name union all select col1,col2,col3 from table2_name;

/*intersect 操作，求两个集合的交集,它将对重复数据进行压缩，且排序*/
select col1,col2,col3 from table1_name intersect select col1,col2,col3 from table2_name;

/*minus 操作，集合减,它将压缩两个集合减后的重复记录, 且对数据排序*/
select col1,col2,col3 from table1_name minus select col1,col2,col3 from table2_name;

/*EXTRACT 抽取时间函数. 此例是抽取当前日期中的年*/
select EXTRACT(YEAR FROM SYSDATE) from dual;
/*EXTRACT 抽取时间函数. 此例是抽取当前日期中的月*/
select EXTRACT(MONTH FROM SYSDATE) from dual;

########################## 增强的 group by 子句 #########################

select [column,] group_function(column)...
from table
[WHERE condition]
[GROUP BY [ROLLUP] group_by_expression]
[HAVING having_expression];
[ORDER BY column]; -------ROLLUP操作字，对group by子句的各字段从右到左进行再聚合

example:
/*其结果看起来象对col1做小计*/
select col1,col2,sum(col3) from table group by rollup(col1,col2);
/*复合rollup表达式*/
select col1,col2,sum(col3) from table group by rollup((col1,col2));

select [column,] group_function(column)...
from table
[WHERE condition]
[GROUP BY [CUBE] group_by_expression]
[HAVING having_expression];
[ORDER BY column]; -------CUBE操作字，除完成ROLLUP的功能外，再对ROLLUP后的结果集从右到左再聚合

example:
/*其结果看起来象对col1做小计后，再对col2做小计，最后算总计*/
select col1,col2,sum(col3) from table group by cube(col1,col2);
/*复合rollup表达式*/
select col1,col2,sum(col3) from table group by cube((col1,col2));
/*混合rollup,cube表达式*/
select col1,col2,col3,sum(col4) from table group by col1,rollup(col2),cube(col3);

/*GROUPING(expr)函数，查看select语句种以何字段聚合，其取值为0或1*/
select [column,] group_function(column)...,GROUPING(expr)
from table
[WHERE condition]
[GROUP BY [ROLLUP] group_by_expression]
[HAVING having_expression];
[ORDER BY column];

example:
select col1,col2,sum(col3),grouping(col1),grouping(col2) from table group by cube(col1,col2);

/*grouping sets操作，对group by结果集先对col1求和，再对col2求和，最后将其结果集并在一起*/
select col1,col2,sum(col3) from table group by grouping sets((col1),(col2));